presence of hemolyzed blood in urine then 1 week after, non hemolyzed blood in the U/A

my father who is 76 years old was admitted for extreme pain in his lower right leg and groin. CBC and U/A was requested and the result for his urinalysis was that there were traces of hemolyzed blood in his urine. He also had lumbosacral xray,pelvis xray ,spinal xray and Kidney, Ureter,Bladder and prostate ultrasound and everything is normal. no masses,no lesions,no stones except for a 5cm cortical cyst in his left kidney but we were told by his sonologist/radilogist that there is no significance with the cyst at the lower pole in his ledt kidney. In his xray, , it revealed degenerative osteoarthrosis.
After a week,my father again had a urinalysis bec of the hemolyzed blood and still presence of NON_HEMOLYZED BLOOD was noted in the result. what could be the problem? is it possible of stones not seen during the ultrasound ?

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